FLEET Velocimetry of Near-Wall Hypersonic Flow Phenomena

Femtosecond laser electronic excitation tagging (FLEET) is demonstrated to probe the near-wall flows around model geometries within Sandia’s Mach 8 Hypersonic Wind Tunnel. A frame-straddling timing sequence allows for the separation of initial and delayed FLEET signals onto two intensified high-speed camera frames. This extends the dynamic range of the measurement to near-zero velocities. A line FLEET configuration is implemented to resolve the wall-normal profiles of the axial-component of velocity. This FLEET acquisition method is demonstrated to characterize two flows: the boundary layer of a seven-degree straight cone and the separation region of a non-canonical cone-slice-ramp (CSR). Within the straight cone boundary layer, freestream Reynolds number is varied to capture the effect of boundary layer transition on the mean and fluctuating velocity profiles. Measurements within 200